Are user directories useful?

The directories at Backflip, Hotlinks and Octopus are hardly useful at all because of meaningless link titles, weak taxonomies and lack of updates. SuperOpenDirectory has much to do to become a useful resource (provided I’m proved wrong, having my doubts about how many people really want to actively publish a directory, as opposed to using a bookmark manager or metabrowser that happens to build a directory in the background). The fact that it exposes the underlying XML (formated in OPML) is a good first step. A search engine is a must (Google?), since SOD (sic) is based on outlines, it might turn results into structures too (as does Vivisimo, a Carneggie Mellonspinoff which recently released an improved beta).